The present invention generally relates to ultrasonic diagnostic apparatuses for ophthalmology and more particularly, to an ultrasonic diagnostic apparatus and method for ophthalmology which use ultrasonic waves suitably for measurement of the axial length and for diagnosis of the intraocular tissue.
When comparison is made between diagnostic apparatuses for ophthalmology and medical ultrasonic diagnostic apparatuses for applications other than ophthalmology (such latter apparatuses are sometimes referred to merely as the non-ophthalmic apparatuses), the ophthalmic apparatuses require probes to be contacted with the eye to be examined. For that reason, the structure and arrangement of the probes are devised in various ways but how ophthalmic apparatuses transmit and receive ultrasonic waves is not especially different from how non-ophthalmic apparatuses operate. In ultrasonic diagnostic apparatuses for ophthalmology, it is not very helpful to only receive the ultrasonic waves reflected by the respective intraocular tissue, process the received ultrasonic signal by a known processing technique, and then indicate the signal on a display in the form of an A-mode waveform or a B-mode image. It is when the measurement data thus obtained is added to the data base on the ophthalmologist's experience that the measurement data can become helpful. of an intraocular iens (an "IOL") inserted after cataract surgery. The calculation of IOL power is carried out by substituting into a power calculation formula the axial length obtained by the ultrasonic diagnostic apparatus. Such IOL power calculations have been formulated based on the ophthalmologist's long-term experience; there now exist 5 such typical formulas. Each of these formulas has merits and demerits. In this way, no single IOL power calculation formula has yet been recognized by a majority of ophthalmologists for its validity. Since the existing formulas have been established based on the individual ophthalmologist's experiences, the formulas tend to vary as the individual opthalmologist's experience is added thereto.
The same applicant as the present application has proposed an ultrasonic diagnostic apparatus for ophthalmology suitable for differential diagnostics in U.S. patent application Ser. No. 313,203 filed on Feb. 21, 1989. This apparatus comprising a means for storing therein a plurality of reflected-echo images having a dynamic range larger than a display image is arranged to retrieve an image of a given condition, which corresponds to the obtained image by adjusting its dynamic range, from the reflection echo images stored in said means. Even in this apparatus, it is impossible to determine what condition is proper for retrieving an image from the storage memory. In other words, the individual ophthalmologist's continual clinical experience is heavily relied upon in using the apparatus for diagnosis, and must be dependable.
In conventional ultrasonic diagnostic apparatuses for ophthalmology, data necessary for various sorts of processings for calculating IOL power, etc. has been stored only in a memory incorporated in a main body. Thus, whenever a new program and its data necessary for diagnostics (e.g., a new IOL power calculation formula) are published, the memory of the main body having the old program and data must be with considerable time and effort changed to substitute in the new program and/or data.
In this way, the operating life of the above prior art apparatus is the same as that of the program and data stored in memory of the main body. However, now that many researchers actively and frequently publish their research results within a short time, it is inconvenient and disadvantageous that the lifespan of the apparatus is influenced directly by the lifespan of the built-in program and data.
Further, with the prior art apparatus having such a disadvantage that, since measured and diagnosed results cannot be stored, an operator cannot measure the next patient until he or she finishes a series of processings and diagnosis with regard to the current patient. This results in other patients being undesirably kept waiting. This also leads to the fact that the ophthalmologist cannot readily make a series of progress examinations because the past measured and diagnosed results of the patients cannot be reproduced in the apparatus. Furthermore, once a diagnosis is finished, the diagnosed results are preserved only in the form of data printed on a paper sheet. Accordingly, when it is desired to use a new program or data, the examination must desirably be restarted from the beginning. In addition, even when the above apparatuses are arranged so as to store diagnosed results therein to some extent, each storage capacity within the apparatuses has its limit. The provision of disk or a large capacity memory built in the apparatus leads unfavorably to the large size and high cost of the apparatus.